A motor-vehicle door latch normally has a housing, a pivotable lock fork on the housing engageable with a door bolt and pivotable between a locked position engaged around the bolt and retaining it on the housing and an unlocked position permitting the door bolt to move into and out of the housing, a release pawl engageable with the fork and displaceable between a holding position retaining the fork in the locked position and a freeing position out of engagement with the fork and permitting the fork to move into the unlocked position, and a lever mechanism connected to the release pawl and movable between an actuated position displacing the pawl into the freeing position and an unactuated position with the pawl in the holding position Inside and outside handles operable from inside and outside the vehicle are connected to the lever mechanism to operate it and unlatch the door.
Inside and outside lock elements are also connected via a common locking lever to this mechanism and are actuatable to prevent at least the outside handle from operating the lever mechanism. Such an arrangement is also often provided with a power actuator that can displace the locking lever to lock and unlock the door centrally and/or remotely.
To prevent a door, normally a rear-seat door, from being accidentally opened, normally by a child, it has become standard to provide a so-called child-safety or -cutout system. This is typically embodied as an element that is exposed at the edge of the door when the door is open and that can be moved between an on and off position. In the on position the inside door handle is no longer operational.
To further prevent that a door can be opened from inside, for instance by a would-be thief who has broken the window to reach into the vehicle, it is known to provide a so-called antitheft system. This system disables the inside locking and latching elements so that the door cannot be unlocked or unlatched from inside. Such an arrangement can also be actuated by the power actuator. Clearly the antitheft and child-safety systems both have in common that they disable the inside door handle, so that these functions are in fact closely related.
In central lock systems it is not normally necessary to provide locking buttons or elements on the rear-seat doors, as the doors are centrally locked and unlocked from the front seat. To open a locked rear-seat door from inside it is therefore standard to set up the lock so that a first actuation of the inside door handle unlocks the door and a second actuation actually unlatches it. This is an important safety feature in that it prevents a locked door from opening if its handle is accidentally actuated once, but still lets an occupant open up a locked door.